The present invention relates to vehicle power control and vehicle speed control systems for vehicles which have an electric drive. The systems include cruise control systems. The vehicles include not only vehicles which are exclusively electric but also vehicles which are hybrid-electric.
In conventional vehicles, the so-called “accelerator pedal” controls power, not speed. If the vehicle includes cruise control to hold the speed of the vehicle constant, cruise control settings are typically determined independently of the position of the accelerator pedal. Commonly, cruise control is engaged by a “set” button pushed by the driver at the desired speed, and disengaged by the driver pressing the brake pedal. A “resume” button returns the vehicle to the set speed.
In some vehicles employing an electric drive (viz. those using an electric motor and an electric motor controller), regenerative braking may store kinetic energy in a battery that would otherwise dissipate as heat. Potential energy released when going downhill may likewise be stored to the battery. Regenerative braking may be initiated by pressing the brake pedal but it also may be activated by release of pressure on the so-called “accelerator pedal”—a somewhat confusing term in the present context, which is hereinafter avoided by instead using the term “power control pedal”.
In more detail, a basic prior art power control system for a vehicle having an electric drive is representationally illustrated in FIG. 1. A somewhat more advanced prior art system is representationally illustrated in FIG. 2. The fundamental difference between the two systems is that the system illustrated in FIG. 2 includes regenerative braking whereas the system illustrated in FIG. 1 does not.
The system shown in FIG. 1 derives power from a battery power source 10 and includes a motor controller 11 and an electric motor 12 for providing motive power to wheels 13 of a vehicle. The system shown in FIG. 2 similarly derives power from a battery power source 10 and includes a motor controller 21 and an electric motor 22 for providing motive power to wheels 13 of a vehicle. Both systems include a power control actuator comprising a power control pedal 25 and a displacement sensor 26 operatively connected to the power control pedal. In both cases, pedal 25 is mounted on a shaft 26.
In each system, pedal 25 is forcibly pivotable (clockwise from the position shown in FIGS. 1 and 2) about an upper horizontal axis a1 (which is also the axis of shaft 26) from a neutral or first pivot position where no power is to be applied to a second pivot position where maximum power is to be applied. The neutral position is maximally anticlockwise and the pedal is rotationally biased to that position by suitable biasing means (not shown). Normally, force is applied to the pedal by a user's foot 100 with the heel rested on floor 101 of the vehicle. When the force is released, then the pedal will return to its neutral position.
In each system, a displacement sensor 27 produces a control signal having a variable value depending on the angular degree of rotation through which the pedal is pivoted clockwise from the neutral position. This signal is provided as an input to the motor controller (11, 21) which in response conditions and provides power from the battery (10, 20) to the electric motor (12, 22) depending on the measured angle.
In the case of the system illustrated in FIG. 1, power control pedal 25 regulates only positive power. Resulting energy flow as depicted by cloud 14 can occur in only one direction from battery 10 to vehicle wheels 13. In the case of the system illustrated in FIG. 2, power control pedal 25 may regulate negative as well as positive power. This is known as “single pedal control.” Here, as depicted by cloud 24 in FIG. 2, energy may flow not only from battery 10 to wheels 13 as in the case of the system illustrated in FIG. 1, but also from wheels 13 to battery 10 when pressure on power control pedal 25 is released.
Power control pedals of the type described above are moveable in only one direction from their neutral position. Hence, they may be characterized as “unidirectional” in their operation. This limits their functionality.
A conventional power control pedal in a vehicle having an electric drive with regenerative braking will not allow the vehicle to coast or freewheel when the foot is removed from the pedal (unless regenerative braking under single pedal control is disabled). Yet freewheeling under such circumstances might be desired.
Also, a conventional power control pedal cannot be used to “set” a desired vehicle speed.